There was a bit of a furore when MGS4 didn't go multiplatform, but the logic was sound: it would have taken far too many discs. Such are the problems you face when you embrace a limited format such as DVDs in the face of much larger competition -- Blu-ray.

For the very same reason, don't expect to see Metal Gear Solid: The Legacy Collection coming to Microsoft's current-gen console, though an appearance on the next one might be feasible.